MENSTRUATION IS ASSOCIATED WITH DISORDERED EXPRESSION OF DESMOPLAKIN I II AND CADHERIN CATENINS AND CONVERSION OF F-ACTIN TO G-ACTIN IN ENDOMETRIAL EPITHELIUM/

Endometrium is unique since it is the only tissue that undergoes regul ar cyclic bleedings, Menstrual shedding is associated with the breakdo wn of endometrium, including the fragmentation of endometrial glands, To gain insight into the underlying basis of fragmentation of the endo metrial epithelium during the menstrual phase, we examined the express ion of proteins implicated in epithelial cell-cell binding in human en dometria throughout the entire menstrual cycle. Western blotting faile d to reveal differences in the relative amount of E-cadherin, alpha- o r beta-catenin or actin in the menstrual endometria compared with thos e in the proliferative or secretory phases, However, specific changes in the expression pattern of these proteins as well as desmoplakin I/I I were detected by immunohistochemical staining in epithelial cells of menstrual endometria, Desmoplakin I/II, E-cadherin, alpha- and beta-c atenins and beta-actin were localized to intercellular borders as well as the luminal and basal regions of glandular epithelium during the p roliferative and secretory phases. Immunoreactivity of E-cadherin and alpha-catenin was confined to epithelial cells, whereas beta-catenin a nd beta-actin were present in epithelial cells, as well as in stroma a nd endothelial cells, Binding of F-actin to fluorescein isothiocyanate -labelled phalloidin localized this form of actin to the intercellular borders, and the basal and luminal cytoplasm of epithelial cells in p roliferative and secretory endometria, Menstrual shedding was associat ed with disorganization of the site-specific distribution of desmoplak in I/II, E-cadherin and alpha- and beta-catenins, This included focal patchy expression of these proteins or their total loss from cell-cell binding sites, as well as loss of F-actin in epithelial cells of mens trual endometrial glands, However, these changes were not observed in the basalis region that is not shed during the menstrual phase. These findings suggest that fragmentation of the endometrial glands during t he menstrual phase is related to the disorganization and/or loss of th e proteins at the adherens and desmosomal junctions, as well as loss o f F-actin.